Device for deriving limited reciprocating motion from rotational motion

ABSTRACT

A device for deriving limited reciprocating motion from a bidirectional electric motor. The device is employed, for example, to reciprocate the plunger of a liquid dispensing pipet to dispense a measured amount of liquid with each reciprocation. The motor drives the plunger upwardly, drawing liquid reagent into the pipet, until an adjustable stop carried by the plunger engages the top flange of the pipet barrel. This causes the motor to reverse and move the plunger downwardly to its bottom limiting position, discharging the measured amount of reagent into a collection receptacle.

United States Patent Shapiro 1 1 7 June 6, 1972 [54] DEVICE FOR DERIVING LIMITED RECIPROCATING MOTION FROM ROTATIONAL MOTION Justin J. Shapiro, Berkeley, Calif. 94710 Dec. 1 l, 1970 Inventor: 1802 Second St.,

Filed:

Appl. No.:

US. Cl ..222/63, 64/275, 74/33, 192/143, 222/158, 222/383, 318/282, 318/286 Int. Cl ..B67d 5/08, F 1 6d 71/00 Field ofSearch 192/143; 74/33,422', 318/282, 318/286, 467; 222/158, 333, 383, 50, 63; 64/275 [56] References Cited UNITED STATES PATENTS 1/1933 Welch ..318/282X 2/1937 Pollok ..318/282 8/1964 Shapiro ..222/383 X Shapiro ..222/383 X Schafer ..222/333 X Crouch.... ....143/6 A Waas ..74/422 Littwin ..318/282 Primary Examiner-Allen D. Herrmann Attorney-Herman L. Gordon ABSTRACT 13 Claims, 5 Drawing Figures I Z l 51- BLcrMAM 5 YA/CHRo/VOUS DEVICE FORDERIVING LIMITED RECIPROCATING MOTION FROM ROTATIONAL MOTION 'This invention relates to devices for deriving limited translatory reciprocatory motion from rotary driving means, and more particularly to a device for deriving reciprocatory motion from a bi-directional electric motor.

A main object of the invention is to provide a novel and improved apparatus for generating limited-reciprocatory motion from a bi-directional electric motor of the type which automatically reverses when it encountersan obstacle, the device being simple in construction, having a wide range of utility, and involving relatively inexpensive components.

A further object of the invention is to provide an improved reciprocatory mechanism driven by a bi-directional electric motor, the device being reliable in operation, being highly versatile, and being usable to automate almost any manually operated system involving a body which must be reciprocated.

A .still further object of the invention is to provide an improved mechanism for deriving limited reciprocatory motion from rotational motion, said mechanism being capable of generating either a single cycle of reciprocation or repeated cycles of reciprocation, as desired.

A still further object of the invention is to provide an improved liquid dispensing device actuated by a mechanism for deriving limited reciprocatory motion from a bi-directional electric motor, the device being adjustable to dispense an accurately measured amount of liquid with each reciprocation, being compact in size, involving relatively few parts, and being easy to operate.

A still further object of the invention is to provide an automated pipet device actuated by a mechanism which derives adjustable limited reciprocatory motion from a bi-directional electric motor, the device being operable either for one measured delivery of a set volume of liquid or for any number of multiples of said set volume up to a desired amount, the adjustment being such that as the device is set for smaller unit delivery volumes the cycle speed is increased, whereby very precise increments of liquid delivery can be obtained within relatively short time periods of operation of the device.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

FIG. 1 is a diagrammatic representation of a generalized embodiment of a device for converting rotary motion into limited reciprocatory motion in accordance with the present invention.

FIG. 2 is a side elevational view, partly in cross-section, of an automated pipet employing a motion conversion device according to the present invention.

FIG. .3 is a fragmentary vertical cross-sectional view taken on line 33 of FIG. 2. I 7

FIG. 4 is a fragmentary horizontal cross-sectional view taken on line 4-4 ofFIG. 2. 1

FIG. 5 is an enlarged fragmentary elevational view taken substantially on the line 5--5 of FIG. 4.

Referring to the drawings, 11 designates a bi-directional synchronous motor of the type described in detail in US. Pat. No. 3,253,169 to A. WfHaydon et alQThis type of motor will start in either direction and will automatically reverse responsive to a moderate rebound upon encountering an obstacle to its rotation. If uni-directional operation of such a motor is desired, a mechanical no-back device may be employed. As examples of this type of motor equipped with no-back devices, reference is made to US. Pat. No. 3,473,058 to R. P. Landgraf et al., US Pat. No. 3,501,658 to E. R. Morley, US. Pat. No. 3,225,874 to L. A. Woolley and US. Pat. No. 3,462,668 to C. RfTompson. In the case of the bi-directional synchronous motor 11 employed in the devices of the present invention, the no-back device is omitted.

Thus, in accordance with the generalized embodiment shown in FIG. 1 diagrammatically representing a typical realization of the presentinvention, the motor 11 is drivingly coupled to a pinion gear 12 which drivingly meshes with a rack bar 13 constrained to move parallel to its length by guides 14, 14 between respective stationary limiting abutment members 15 and 16. If the motor 1 1 is continuously energized, the rack bar 13 will reciprocate with a strokedetermined by the difference between the spacing of the abutment members 15, 16 and the length of the rack bar 13. v

The reciprocation of the rack bar 13 may be limited to one cycle by the provision of a limit switch 17 connected in series with one of the motor leads. Limit switch 17 is normally closed and is opened by an abutment arm 38 carried by the lower end of the rack bar 13when said rack bar reaches the lower end of its stroke, namely, when it engages the bottom abutment member 16. A manually operated starting switch 18 connected in parallel with limit switch 17 may be employed to initiate operation of the device. Switch 18 may be of the momentary-contact type to provide a single cycle of operation, or may be of a type which can be held closed, for providing a desired period of repeated reciprocation cycles of rack bar 13.

Other well-known equivalent mechanisms for developing reciprocating motion may be employed in place of the rack and pinion mechanism of FIG. 1 within the spirit of the present invention.

Referring now to FIGS. 2 to 5, 19 designates a conventional burette device, for example, a liquid dispensing device similar to that disclosed in US. Pat. No. 3,211,335 to J. J. Shapiro. This burette device has a barrel 20 integrally formed at its top end with a flange 21. Slidably and sealingly engaged in the barrel 20 is the syringe plunger 22, said plunger having eccentrically and rigidly secured to its top end the relatively large operating disc 23. Rigidly secured to a marginal portion of disc 23 is a depending rod 24 which extends parallel to and adjacent to the barrel 20 and is provided with the adjustable stop collar 25 defining an abutment element, said collar being engageable with top flange 21 to limit upward extension of plunger 22. The collar is provided with a downwardly divergent frusto-conical bottom flange 26 extending adjacent a volumetric scale 27 inscribed on barrel 20. The collar is further provided with a clamping screw 28 to lock it in an adjusted position on rod 24, said position corresponding to a predetermined desired discharge volume of the burette apparatus, as indicated by the flange 26 on scale 27 when the plunger 22 is in its lowermost position, as shown in FIG. 2.

The barrel portion 20 is formed integrally with an enlarged hollow bottom stopper member 29 sealingly engageable in the neck 30 of a conventional reagent bottle 31. The burette device 19 is further provided with an outlet conduit 32 which may include a check valve, and with an inlet conduit also provided with a check valve, the inlet conduit depending through the stopper portion 29, as described in detail in the abovementioned US. Pat. No. 3,211,335.

In accordance with the present invention, a support means comprising, for example, a pair of parallel clamping blocks 33, 34 are engaged around the lower portion of barrel 20, the blocks being formed with opposed semi-cylindrical notches 35 and 36 to receive the barrel. A resilient liner 37 may be provided between notches 35, 36 and barrel 20. Clamping screws 39, 39 are engaged through block 34 on opposite sides of barrel 20 and are threadedly engaged in tapped bores 40 provided in block 33. A vertical upstanding support plate 41 is rigidly secured to block 33 by bolts 42, 42 threadedly engaged in tapped bores 40 opposite to clamping screws 39, cylindrical spacer sleeves 43, 43 being provided on bolts 42, 42 between plate 41 and block 33.

The motor 11 is mounted on the upper portion of plate 41. A rack bar 13 is rigidly connected to the lower end of rod 24 by a coupling sleeve 44. A pinion gear 12 is resiliently secured on the output shaft of motor 11 and meshes with rack bar 13, as is shown in FIG. 3. Thus, pinion gear 12 is rotatably mounted on shaft 45 and is resiliently connected thereto by a generally circular spring 50 having one end secured at 51 to gear 12 and the other end provided with an arm 52 secured to shaft 45, as shown in FIG. 5. The resilient connection of gear 12 to shaft 45 permits the generation of the required moderate amount of rebound necessary to cause motor 11 to reverse its direction of rotation.

A flanged guide roller 46 is journalled to plate 41 and supportingly engages rack bar 13 at the edge thereof opposite to pinion gear 12, as shown in FIG. 3. Flanged roller 46 thus guides rack bar 13 for vertical reciprocation.

A limit switch 17 is mounted on block 33 with its operating lever 47 in a position to be engaged by the bottom end of rack bar 13 when disc 23 engages flange 21 at the bottom end of the stroke of plunger 22. Thus, the bottom end of rack bar 13 acts in the manner of arm 38 in FIG. 1 to open the normally closed limit switch 17. The electrical circuit associated with motor 1 1 may be similar to that shown in FIG. 1.

In operation, the stop collar is set to provide a desired discharge volume per cycle of plunger 22 using scale 27. With the plunger 22 in its lowermost position, namely, with disc 23 engaging flange 21, switch 18 is closed for a period sufflcient to cause motor 11 to be energized and to allow switch 17 to close. The motor will operate in a direction to elevate plunger 22 and draw the desired volume of liquid from container 31 into barrel 20. When collar 25 engages flange 21 the motor 11 will reverse and cause plunger 22 to descend, discharging the desired volume of liquid into a suitable receiving receptacle through outlet conduit 32. At the end of the discharge stroke of plunger 22, switch 17 will be opened, causing motor 11 to become deenergized.

Switch 18 may be held closed to provide any desired number of strokes of plunger 22. The operation of switch 18 may be controlled by any suitable conventional timer means to provide a selected number of strokes of plunger 22.

It will be noted that when the collar 25 is set for smaller unit delivery volumes, the cycle speed is increased, whereby very precise increments of liquid delivery can be obtained within relatively short time periods of operation of the apparatus.

While a specific embodiment of an automated buret or pipet device has been disclosed in the foregoing description, it will be understood that the apparatus may be embodied in various other applications where it is desired to derive limited reciprocatory motion from rotational motion. Therefore it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

1. In combination, an apparatus having a linearly reciproca tory operating member, stop means limiting translation of said operating member between opposite limits of travel, a bidirectional motor of a type having means to automatically reverse it responsive to encountering an obstacle, and means drivingly coupling said motor to said operating member, and wherein said apparatus comprises a pipet having a barrel and said operating member comprises a plunger in said barrel.

2. The structural combination of claim 1, and means to adjust said stop means to vary the travel stroke of said operating member.

3. The structural combination of claim 1, and wherein said motor is provided with an energizing circuit including a limit switch, and means operating said limit switch at an end of the travel stroke of said operating member,

4. The structural combination of claim 3, and control switch means connected across said limit switch,

5. The structural combination of claim 1, and wherein the means drivingly coupling the motor to said operating member comprises rack bar means on the operating member and pinion gear means on the motor meshingly engaged with said rack bar means.

6. The structural combination of claim 1, and wherein said stop means includes a disc member at the top' end of said plunger engageable with the top end of said barrel, said barrel top end being formed with a flange, said disc member having depending rod means, and an abutment element on said rod means engageable with said flange.

7. The structural combination of claim 6, and means to adjust the position of said abutment element on said depending rod means.

8. The structural combination of claim 1, and wherein said means drivingly coupling said motor to said operating member comprises rack bar means ri idly connected to said plunger, said motor being mounted su stantrally rigidly relative to said barrel, and drive pinion gear means on the motor meshing with said rack bar means.

9. The structural combination of claim 8, and wherein said motor is provided with an energizing circuit including a limit switch, said rack bar means being provided with means operatively engageable with said limit switch at the end of the discharge stroke of said plunger.

10. The structural combination of claim 9, and control switch means connected in parallel with said limit switch.

1 l. The structural combination of claim 8, and wherein said drive pinion gear means comprises a pinion gear mounted on and resiliently connected to the shaft of the motor.

12. The structural combination of claim 8, and wherein the motor is provided with an upstanding supporting member secured to the barrel, and flanged guide roller means journalled to said supporting member and supportingly engaging said rack bar means opposite said drive pinion gear means.

13. The structural combination of claim 12, and wherein said drive pinion gear means comprises a pinion gear journalled on the shaft of the motor and an arcuate coupling spring connecting said pinion gear to said motor shaft, whereby to provide a resilient driving connection between the motor and the pinion gear.

* k II 

1. In combination, an apparatus having a linearly reciprocatory operating member, stop means limiting translation of said operating member between opposite limits of travel, a bi-directional motor of a type having means to automatically reverse it responsive to encountering an obstacle, and means drivingly coupling said motor to said operating member, and wherein said apparatus comprises a pipet having a barrel and said operating member comprises a plunger in said barrel.
 2. The structural combination of claim 1, and means to adjust said stop means to vary the travel stroke of said operating member.
 3. The structural combination of claim 1, and wherein said motor is provided with an energizing circuit including a limit switch, and means operating said limit switch at an end of the travel stroke of said operating member.
 4. The structural combination of claim 3, and control switch means connected across said limit switch.
 5. The structural combination of claim 1, and wherein the means drivingly coupling the motor to said operating member comprises rack bar means on the operating member and pinion gear means on the motor meshingly engaged with said rack bar means.
 6. The structural combination of claim 1, and wherein said stop means includes a disc member at the top end of said plunger engageable with the top end of said barrel, said barrel top end being formed with a flange, said disc member having depending rod means, and an abutment element on said rod means engageable with said flange.
 7. The structural combination of claim 6, and means to adjust the position of said abutment element on said depending rod means.
 8. The structural combination of claim 1, and wherein said means drivingly coupling said motor to said operating member comprises rack bar means rigidly connected to said plunger, said motor being mounted substantially rigidly relative to said barrel, and drive pinion gear means on the motor meshing with said rack bar means.
 9. The structural combination of claim 8, and wherein said motor is provided with an energizing circuit including a limit switch, said rack bar means being provided with means operatively engageable with said limit switch at the end of the discharge stroke of said plunger.
 10. The structural combination of claim 9, and control switch means connected in parallel with said limit switch.
 11. The structural combination of claim 8, and wherein said drive pinion gear means comprises a pinion gear mounted on and resiliently connected to the shaft of the motor.
 12. The structural combination of claim 8, and wherein the motor is provided with an upstanding supporting member secured to the barrel, and flanged guide roller means journalled to said supporting member and supportingly engaging said rack bar means opposite said drive pinion gear means.
 13. The structural combination of claim 12, and wherein said drive pinion gear means comprises a pinion gear journalled on the shaft of the motor and an arcuate coupling spring connecting said pinion gear to said motor shaft, whereby to provide a resilient driving connection between the motor and the pinion gear. 